在双打比赛中需要关注，比赛台面上的白色中线所属区域。双打时，白色中线应视为左半区的一部分。发球时，球应先后触及发球员和接发球员的左半区。Doubles match needs the white center line on the playing suce. The center line shall be regarded as part of each left half-court. the served ball shall touch successively the left half court of server and receiver.